Manufacture of aluminium in high power tanks



May 8, 934 P J, M TORCHE-- 3,958,323

MANUFACTURE OF ALUMINIUM IN HIGH POWER TANKS Filed NOV. 19, 1931Patented Moy 8, 1934 UNITED VSTATES PATENT OFFICE etElectrometallurgiques Olais, Froges et Camargue, Paris, France, acorporation o! France Application November 19, 1931, Serial No. 576,153In France October 21, 1931 s claims. (c1. zei-2o) Aluminium is generallymanufactured, through electrolysis, in rectangular or round vessels, thebottom of which forms the cathode, and which comprise a plurality ofblocks of coal previously baked which serve as anodes and are usuallyfrom 10 to 14 in number and even more.

The use of multiple anodes of the usual type involves diilicultiesconcerning their good adjustment, which is necessary in order to insurea good distribution of the current, and consequently a satisfactoryoutput. Moreover, mounting said previously baked anodes involves a largeconsumption thereof, as considerable waste results from that operation.

It has been endeavoured to reduce that consumption by the use ofcontinuous electrodes (that is to say of vertically mounted electrodesthe lower ends of which are immersed in the electrolytic bath, whiletheir upper ends are lengthened as their lower ends are wearing oi) ofany type whatever, notably the so-called Soderberg electrode, which isof the self -baking type, and of circular transverse section, incircular tanks. A considerable advantage of said continuous electrodesislthat the tank, comprising only one anode, is much easier to managethan tanks containing a plurality of anodes. However, twoconsiderations, one of which is technical and the other economical,prevent the use of said continuous electrodes from spreading rapidly.From a technical point of view, as lsoon as great intensities of currentare used, and even for an intensity as low as 18,000 amperes, the largediameter which the electrode must be given prevents the easy evacuationof the gases produced by the electrolysis, and the satisfactory workingof the apparatus. It further causes overheating of the central part ofthe bath, below said electrode of large diameter, and this isprejudicial to a good output.' Various means for obviating suchdrawbacks have been suggested, for instance providing channels insidethe electrodes or giving an annular shape to the latter, or again,sepa-` rating said electrodes into two parts with a space between them,but such arrangements are, in certain instances, complicated andexpensive, and in other cases, inefcacious.

From an economical point of view, the necessity of replacing the usualrectangular shaped tanks by round shaped tanks involves discarding aconsiderable equipment. This is obviously a great obstacle to the promptadoption of continuous electrodes having circular transverse sections,of any type whatever.

My invention makes it possible to obviate the above mentioned drawbacksby the use, in electrolytick apparatus of great power, and in fact ofunlimited power, and more particularly in apparatus comprising arectangular tank, of a continuous anode or of a limited number ofcontinuous anodes, preferably of rectangular, or substantiallyrectangular, section, one of the dimensions of which is substantiallysmaller than the other dimension. In order to avoid the above mentioneddrawbacks, it is suiiicient that the transverse section of the electrodeshould not exceed a certain limit in one of its dimensions. The usefulsurface which is necessary for the electrode may be maintained byincreasing the other dimension.

In the Figs. l and 2 of the drawing I have 70 diagrammatically shown inplan view an electrolytic apparatus according to my invention. The outervessel, whose bottom forms the cathode, is shown at 2, while thecontinuous anode or anodes of elongated rectangular shape is or areshown at 1.

Owing to the rectangular or elongated shape of the electrodes, the gasesproduced during the electrolytic` process find a short way of escape andthe overheating of the central part of the bath is either wholly doneaway with or so reduced that any detrimental action is no longer to befeared in this respect. 'Ihe rectangular tanks already in use can beemployed as in the past and it is no longer necessary to e'ect anyalteration of the 85 plant beyond that of the anodic apparatus.

Lastly, and this constitutes a highly important advantage, there is nownothing to prevent the increase, in large proportions, of the power oroutput of the apparatus, which in fact becomes practically unlimited, asit sufces to increase the length of the tanks by increasing the numberof continuous anodes with which they are provided.

On the other hand, such an electrode is readily handled and adjusted,and, on account of the great intensity of the current which flowsthrough it, it may be provided, quite economically, with electriccontrollingY instruments, whereas such an expense would be absolutelyprohibitive in the case of multiple electrodes Working under lowamperage, such as are used at the present time. Under these conditions,it is easy to control a small number of continuous electrodes of thattype, and the eventual use of two such electrodes instead of 10, 14, oreven 20 of the electrodes previously employed may be considered with thetanks of the largest type actually utilized for practical purposes. Theoutput thus obtained and the ease with which the apparatus may becontrolled are notably superior to the results obtained either with asingle continuous electrode of cylindrical shape or with multipleelectrodes working under low arnperage.

Experience has proved that the above mentioned results can be easilyimproved upon and that the power may be increased while allowing theapparatus to be run with the greatest facility. Thus a three electrodetank, adapted to be used with a current of 45,000 amperes has beenconstructed, the output of which, from all points o! view, was clearlysuperior to that of all of the apparatus for manufacturing aluminiumthat are now in use, not only as regards the consumption of current, butalso as regards the consumption of electrode paste and the hired laborthat is required. These experiments prove that apparatus of high powerare quite advantageous for practical purposes, while, up to the presenttime, the use of such apparatus had met with working diilculties whichhad not yet been overcome.

What I claim is:

1. A high power electrolytic furnace for the production of aluminium,which comprises in combination, a tank of substantially rectangularhorizontal section, the bottom of which acts as a cathode, and acontinuous anode of elongated horizontal section placed in said tank,one of the horizontal sectional dimensions of said anode being at themost equal to the maximum dimension permitting the disengagement ofgases from beneath the active surface of the anode and preventingsuperheating of the aluminium beneath the active surface of said anode.

2. A high power electrolytic furnace for the production of aluminium,which comprises in combination, a tank of substantially rectangularhorizontal section the bottom of which acts as a cathode, and acontinuous anode of elongated horizontal section placed in said tank,said anode having the shorter one of its horizontal dimensions at themost equal to the maximum dimension permitting the disengagement ofgases from beneath the active surface of said anode.

3. A high power electrolytic furnace for the production of aluminium,which comprises in combination, a tank of substantially rectangularhorizontal section the bottom of which acts as a cathode, and alcontinuous anode of elongated horizontal section placed in said tank,said anode having the shorter one of its horizontal dimensionsV at themost equal to the maximum dimension preventing superheating of thealuminium beneath the active surface of said anode.

PIERRE JEAN MICHEL TORCHET.

